For those residing in Europe or other countries, it depends on that individual tax laws of the countries. Some places in Europe for example may treat it as a normal capital gain while others may classify it as gambling, which means no taxes. Check with the authorities.
You have to report 1 or both forms if you meet the threshold asset value... If you are confused, just look up "FATCA". Here is the Form 8938...http://www.irs.gov/pub/irs-pdf/f8938.pdf.......................................... and here is the form most will need if they have over $10,000 account...http://www.fincen.gov/forms/files/FBAR%20Line%20Item%20Filing%20Instructions.pdf
Reporting Threshold (Total Value of Assets)
|Form 8938, Statement of Specified Foreign Financial Assets
$50,000 on the last day of the tax year or $75,000 at any time during the tax year (higher threshold amounts apply to married individuals filing jointly and individuals living abroad)
|FinCEN Form 114, Report of Foreign Bank and Financial Accounts (FBAR)|
$10,000 at any time during the calend
If it's under $1,500, it will just be taxed at your marginal tax rate. However, if it's over $1,500 than you put it on schedule B and it ends up with a maximum tax rate of 20% no matter how much you make. In my readings on these forms, it showed all kinds of possible income types including interest, which is what most traders would be worried about reporting on.
Have fun and get trading.